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87 lines
2.7 KiB
C
87 lines
2.7 KiB
C
/*
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* JFFS2 -- Journalling Flash File System, Version 2.
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*
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* Copyright (C) 2001 Red Hat, Inc.
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*
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* Created by Arjan van de Ven <arjanv@redhat.com>
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*
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* The original JFFS, from which the design for JFFS2 was derived,
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* was designed and implemented by Axis Communications AB.
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*
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* The contents of this file are subject to the Red Hat eCos Public
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* License Version 1.1 (the "Licence"); you may not use this file
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* except in compliance with the Licence. You may obtain a copy of
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* the Licence at http://www.redhat.com/
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*
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* Software distributed under the Licence is distributed on an "AS IS"
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* basis, WITHOUT WARRANTY OF ANY KIND, either express or implied.
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* See the Licence for the specific language governing rights and
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* limitations under the Licence.
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*
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* The Original Code is JFFS2 - Journalling Flash File System, version 2
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*
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* Alternatively, the contents of this file may be used under the
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* terms of the GNU General Public License version 2 (the "GPL"), in
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* which case the provisions of the GPL are applicable instead of the
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* above. If you wish to allow the use of your version of this file
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* only under the terms of the GPL and not to allow others to use your
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* version of this file under the RHEPL, indicate your decision by
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* deleting the provisions above and replace them with the notice and
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* other provisions required by the GPL. If you do not delete the
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* provisions above, a recipient may use your version of this file
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* under either the RHEPL or the GPL.
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*
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* $Id: compr_rtime.c,v 1.2 2002/01/24 22:58:42 rfeany Exp $
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*
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*
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* Very simple lz77-ish encoder.
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*
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* Theory of operation: Both encoder and decoder have a list of "last
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* occurances" for every possible source-value; after sending the
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* first source-byte, the second byte indicated the "run" length of
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* matches
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*
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* The algorithm is intended to only send "whole bytes", no bit-messing.
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*
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*/
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#include <config.h>
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#include <jffs2/jffs2.h>
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void rtime_decompress(unsigned char *data_in, unsigned char *cpage_out,
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u32 srclen, u32 destlen)
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{
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int positions[256];
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int outpos;
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int pos;
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int i;
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outpos = pos = 0;
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for (i = 0; i < 256; positions[i++] = 0);
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while (outpos<destlen) {
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unsigned char value;
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int backoffs;
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int repeat;
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value = data_in[pos++];
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cpage_out[outpos++] = value; /* first the verbatim copied byte */
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repeat = data_in[pos++];
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backoffs = positions[value];
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positions[value]=outpos;
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if (repeat) {
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if (backoffs + repeat >= outpos) {
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while(repeat) {
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cpage_out[outpos++] = cpage_out[backoffs++];
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repeat--;
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}
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} else {
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for (i = 0; i < repeat; i++)
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*(cpage_out + outpos + i) = *(cpage_out + backoffs + i);
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outpos+=repeat;
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}
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}
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}
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}
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